Delivery reports are a convenience feature that lets the sender know if the message they sent has been received (not read) by the recipient's device (for this, it has to be online and have sufficient storage space, though modern phones usually have so much storage the latter is no problem at all).
Every single phone I ever had, from early Nokias in the 00s to Androids and iPhones, had it disabled by default. While feature phones often delivered these reports with a pop-up and sometimes notification sound, which some people could deem annoying, this trend continues even with smartphones, which typically display it merely as an indicator in the chats list of your messaging application.
So, is there an actual reason why it's turned off by default everywhere? The feature has to be enabled on the sender's device to receive these and the recipient has no way of opting out of this, so it's not a privacy thing by any means.
UPD: Apparently, carriers in some countries charge customers for receiving delivery reports as if they were sent messages. I've never realized this - reports always were absolutely free where I live. Thank you for your responses!
I don't consider resorting to (any) ad trackers being an ethical way to earn revenue. First, because the site/app owner doesn't really have much control over the relevancy or legitimacy of ads shown to users (ad network admins may be doing their best, but scams will still make their way through - hey there, Unity Ads). Second, no, I'm not letting you to fingerprint me across basically all websites I visit to enhance ad relevance, since most of it ends up being like intrusive thoughts anyway, with no real use for me. In the end, it's just distracting, annoying garbage cluttering the view. I'm sorry I couldn't explain my position better.
The internet was better when the only kind of ads out there was contextual, for money or just by friendship. "Hey, so you're on my site reviewing various types of coffee? Check out my aunt's coffee shop in Prague, they're making excellent cappuccino! Click here to visit their site!"
Likewise, I would much rather prefer a service with limited functionality (e.g. ability to download only the latest version of an app in this case) in its free version to a service that throws a pile of shit at you, then asks if you want to clean yourself from it for a monthly (quarterly, yearly) fee.